I think your room is beautiful, warm and inviting as is. I think the fireplace is lovely as it is too. I'm wondering if swapping the positions of the sofa and matching (?) chairs would address the light and artwork issues you mentioned. You could put the small table with the lamp between the two chairs, bringing that light source more toward the center of room, which I think will illuminate the space a bit better. It's hard to tell from the photo, but It seems like putting the sofa on the longer wall would allow you to add a floor lamp at end of the sofa (the end near the checked chair) to bring light to that end of the room, while also leaving an unbroken space for art work on the long wall.

So you could do a sectional, provided you select one that doesn't extend beyond the limit of your windows on each wall and that is simple in its details.

Your floor is nice and with the style of your furniture, etc., you don't necessarily need a rug. I think I would bring in an Ottoman coffee table with a pattern and that would give enough visual interest. https://www.wayfair.com/furniture/pdp/trent-austin-design-vanpelt-ottoman-trnt3383.html?piid%5B0%5D=41224925&piid=41224925

To try to answer your questions...two armchairs facing away from a room's entrance do not block anything visually. Try this: Leave the blue chairs where they are. The sofaback facing the big wall and the square stools in front of the windows and the entertainment console will be right there under the windows so you can sit and access it. As a hangout/music room there will be clutter with all the gear. Get a large coffee table with lots of storage. Get your bookcase with storage doors. Your guitars and ukes can hang on a wall next to the key board. I think you're okay if you still want to revisit that concept. This is a concept rendering and not to scale. I included the keyboard in the upper left and bookcase lower right. The windows are the blue line at the top and the console and speakers with it. Parthenon Coffee Table By Kelly Clarkson Home shown in Turquoise and Vintage White